Muhlenbergia 5: 86. 1909.
Herbs or subshrubs, perennial, 2.7–8 dm; from a small, woody caudex; with thick, woody roots. Stems several to many, erect to sprawling, usually profusely branched, including many small, leafy axillary shoots, hairs dense, retrorse, medium length, stiff, eglandular, distally spreading, long, soft, sometimes matted, very short-glandular. Leaves green, linear-lanceolate, distally sometimes broadly lanceolate, 2–4.5 cm on main branch, 0.5–1 cm on proximal part of side branches, not fleshy, margins plane, involute, sometimes flat, 0-lobed, apex acute to acuminate. Inflorescences 2–4.5 (–14 in fruit) × 1.5–4 cm; bracts proximally greenish, distally red to reddish orange, broadly lanceolate to oblong, 0 (–3) -lobed; lobes ascending, lanceolate, short, arising above mid length, apex acute to obtuse. Calyces proximally pale green to pale yellow-green, distally pale-red to red-orange above middle, 12.5–20.5 mm; abaxial and adaxial clefts 6–9 mm, 33–50% of calyx length, deeper than laterals, lateral (1.5–) 3–4 mm, 20–35% of calyx length; lobes lanceolate or broadly triangular, apex acute. Corollas slightly curved, 15–24 mm; tube 10–13 mm; beak exserted, adaxially green, 6–10 mm; abaxial lip green, reduced, slightly pouched, sometimes visible in front cleft, 0.5–1.5 mm, 15–20% as long as beak; teeth incurved, white or green, 0.4–0.7 mm.
Phenology: Flowering Jun–Oct.
Habitat: Rocky slopes, shaded canyons, riparian zones, open conifer forests, sun or partial shade.
Elevation: 1500–2500 m.
Castilleja organorum is endemic to the Organ Mountains of Doña Ana County. Reports from the mountains of the Mogollon Rim of east-central Arizona and adjacent New Mexico are based on specimens of C. nelsonii. Castilleja organorum is grouped with C. linariifolia by some authors (for example, G. L. Nesom 1992c), but it has subequal abaxial and adaxial calyx clefts and is more likely closely related to C. integra. Castilleja organorum differs from the latter species in its loose, often profusely branched habit, more compact inflorescences, and usually smaller corollas. In Fillmore Canyon, C. integra, C. lanata, and C. organorum are all found, but each is in a different habitat, and there is no sign of hybridization.
"arising" is not a number.